When the Buffalo Bills gave Mario Williams $50 million guaranteed in March, they expected to see immediate returns on the investment. Instead, all they have to show for it is the worst defense money can buy.

Tennessee is the only team to allow more points through seven games, and the Titans just beat the Bills, 35-34, on Sunday. Only the New Orleans Saints have given more yards per game than the Bills. Here are the most alarming stats: Buffalo is giving up a league-worst average 176.9 rushing yards per game and an astonishing 6.0 yards per carry.

With the signing of Williams at defensive end and a transition back to a four-man front, the Bills were supposed to field one of the game's strongest lines. Williams and former New England Patriots end Mark Anderson ($8 million guaranteed) were supposed to help their two talented tackles—2011 third overall pick Marcell Dareus and former Pro Bowl selection Kyle Williams—thrive more inside.

There has been plenty of heat on coach Chan Gailey for the team's offensive miscues, but the defense has been the true bugaboo in Buffalo under coordinator Dave Wannstedt. It's preventing the team, at 3-4, from even thinking about being a playoff contender.

Consider that just two years ago, the Bills had Perry Fewell in Wannstedt's post. All Fewell has done since he was fired in Buffalo is to mold the New York Giants' defense into Super Bowl champions for a second time.

Personnel and scheme deserve equal blame for the Bills' mess. It's just another sign that a franchise working on its unlucky 13th season without a playoff appearance doesn't have a good grasp of how to turn things around.

Williams was given a $96 million contract over six years. This year, he has only 3 1/2 sacks in seven games, with two coming in Week 6 against the Arizona Cardinals, a team that can't pass-protect against a tackling dummy at the moment. But he got the big deal because he was more than just a pass rusher, a strong all-around end who would stuff the run, too. That obviously isn't happening, either.

There is the question of how much Williams has been hampered by a banged-up wrist, an injury the Bills had been enigmatic about reporting. Anderson gets a bit of a pass because he's actually missed time with a knee injury. Bottom line, that's a lot of money not playing well or not playing at all.

The position Wannstedt used to coach before his promotion, linebackers, hasn't given the Bills any solid play. It's become too easy for dynamic rushers such as the Titans' Chris Johnson to blow through the second level for plays like his 83-yard touchdown run.

The Bills have a pair of highly skilled safeties, George Wilson and Jairus Byrd, but they're rendered ineffective as playmakers when they're called upon to clean up against the run—they already have a combined 85 tackles this season.

Before Week 7, the defensive woes led to desperation. Shawne Merriman, who didn’t work out as a reclamation project to rush the passer as a 3-4 outside linebacker for the Bills, was re-signed to fill in for Anderson at 4-3 end.

Square peg, meet round hole. In a short time, the Bills have gone 4-3 to 3-4 back to 4-3 again. They thought splashy spending was the best way to usher in their latest alignment adjustment. They thought it would be a quick fix for them to suddenly handle the offensive juggernaut of the AFC East, the New England Patriots.

The Patriots slammed the door on that notion by routing the Bills, 52-28 at Buffalo in Week 4. We should have seen that result coming, when the far less explosive New York Jets similarly drubbed the Bills, 48-28 in Week 1.

The Bills' ill-advised signing of Williams goes back to fundamental problem—a lack of patience to come out of a dozen years of futility. Last year, it was paying Ryan Fitzpatrick like the franchise quarterback he really isn't.

You can't act like you're reloading when you really need to keep rebuilding.

Take the Miami Dolphins. They're just as tired with the Patriots dominating the division but they were smart to go with a rookie coach and rookie quarterback this season and now there's actual promise in South Florida. The Dolphins also made a more modest free-agent investment in a former 2006 draft star, as running back Reggie Bush has earned every bit of his contract.

Watching the Bills get run over week after week, it's easy to put a finger on their current woes. Maybe they'll finally figure out the hard way that trying to plug a hole here and there doesn't do much to stop a much bigger leak.